Molecular phenotyping of cell types and neural circuits underlying pathological neuropsychiatric conditions and their responses to therapy provides one avenue for the development of more specific and effective treatments. In this study, we identify a cell population in the cerebral cortex that shows robust and specific molecular adaptations following long-term SSRI treatment. We employed the bacTRAP strategy, which uses BAC transgenic mice expressing EGFP-tagged ribosomal protein L10a in specific cell populations, to affinity purify polysome-bound mRNAs from S100a10-expressing corticostriatal projection neurons. We show that the S100a10 cells are a unique population of cortical cells that are strongly and specifically responsive to chronic SSRI administration and that this response requires p11 (the protein product of S100a10). Our data demonstrate that the beneficial actions of antidepressant therapy can be mediated by a single cell type that is positioned to normalize activity between cortical and subcortical sites, and suggest that development of drugs that specifically target the activity of these cells may result in improved therapies to treat depression. S100a10 bacTRAP mice were administered either fluoxetine (FLX) or vehicle (VEH) in their drinking water for 15-18 days. Three independent TRAP replicates from the cortex of each group were then collected. Total RNA from the immunoprecipitates was amplified and hybridized. Data were normalized with the GCRMA algorithm and replicates were averaged across conditions. We recommend filtering data to remove probe sets with normalized expression values less than 50 in at least one condition. Because the S100a10 BAC labels some non-neuronal cells, we recommend only probe sets listed in Table S1 of the accompanying paper be included in the analysis.